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03-03-2009, 03:26 PM   #1
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My K20D on it self corrects aperture !

I noticed today when shooting the sun behind clouds, with my new DA 55-300, that my K20D, on it self, corrected the aperture from 5.6 to 18 despite I was in Av mode !
The aperture was set back to 5.6 after the shot.

The shutter speed was 1/4000" at 200iso. Click the image to see it on black !




Last edited by fs999; 03-03-2009 at 03:44 PM.
03-03-2009, 03:44 PM   #2
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That is almost certainly the result of setting the custom function "Auto EV compensation" to "On".

Last edited by RBellavance; 03-03-2009 at 04:53 PM.
03-03-2009, 03:47 PM   #3
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That's an important feature ! Very intelligent !
03-03-2009, 03:53 PM   #4
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QuoteOriginally posted by RBellavance Quote
That is almost certainly the result on setting the custom function "Auto EV compensation" to "On".
Beat me to it.

Custom Settings Menu -> 10. Auto EV Compensation

03-03-2009, 04:44 PM   #5
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QuoteOriginally posted by fs999 Quote
That's an important feature ! Very intelligent !
It can make sense. If you don't want to care if your Av setting is possible within bright light.
However, in your sample, the image is underexposed, too...

EDIT:
Ah, I now see, why. You dialed in an exposure correction of -4EV.
So, if ISO200, 1/4000, f/5.6 and -4EV was a mission impossible, why do you complain your K20D made the best out of it?
03-03-2009, 10:21 PM   #6
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Falconeye - Could not the -4EV be the result of the Auto EV compensation?

Jack
03-03-2009, 11:18 PM   #7
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QuoteOriginally posted by jbinpg Quote
Falconeye - Could not the -4EV be the result of the Auto EV compensation?

Jack
Based on my brief tests last week the Auto EV is done through aperture adjustment, at least if you're in AV mode.

Chris
03-03-2009, 11:48 PM   #8
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scary future

The cameras starts to do our work



03-04-2009, 01:30 PM   #9
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QuoteOriginally posted by sinnettc Quote
Based on my brief tests last week the Auto EV is done through aperture adjustment, at least if you're in AV mode.

Chris
that makes no sense

what's the point of av then?
03-04-2009, 02:01 PM   #10
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QuoteOriginally posted by falconeye Quote
However, in your sample, the image is underexposed, too...
I would say it is correctly exposed for not blowing highlights... Did you look at the photo on black ?

QuoteOriginally posted by falconeye Quote
So, if ISO200, 1/4000, f/5.6 and -4EV was a mission impossible, why do you complain your K20D made the best out of it?
I am certainly not complaining, I was astonished, that's all
03-04-2009, 02:08 PM   #11
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QuoteOriginally posted by kristoffon Quote
that makes no sense

what's the point of av then?
This "Auto EV compensation" function (if enabled!) only kicks in where the chosen exposure parameters get "out of bounds" (eg. if the shutter speed would exceed 1/4000s, for instance).
03-04-2009, 05:03 PM   #12
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QuoteOriginally posted by jbinpg Quote
Falconeye - Could not the -4EV be the result of the Auto EV compensation?

Jack
No. Exif says -4EV exposure compensation was active (EXIF field 9204 "ExposureBiasValue"). But I invite you to google what can influence this value (except dialing it in).

Auto EV compensation (as I understand it -- and I can be wrong) actually is no compensation. The opposite, actually. It tries to maintain a correct EV exposure value by changing "the other parameter" if the predefined paramater (exposure time or aperture) has reached its limiting value.

Therefroe, with 1/4000s and -4EV, the camera had to ignore the f/5.6 setting and aim for something smaller.

The -4EV, in the first place, are most probably a simple user error...


EDIT...

I had a look at the EXIFs again. This image was the darkest in a bracketed exposure series. fs999 "forgot" to tell us about and I'm not amused... So, the -4EV wasn't dialed in but choosen by the bracket series. All else as I've said.

Last edited by falconeye; 03-04-2009 at 05:10 PM.
03-05-2009, 06:45 AM   #13
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QuoteOriginally posted by sinnettc Quote
Based on my brief tests last week the Auto EV is done through aperture adjustment, at least if you're in AV mode.

Chris
That would explain why I've never been able to get it to do a damned thing with a Takumar mounted.
03-05-2009, 12:18 PM   #14
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QuoteOriginally posted by falconeye Quote
I had a look at the EXIFs again. This image was the darkest in a bracketed exposure series. fs999 "forgot" to tell us about and I'm not amused... So, the -4EV wasn't dialed in but choosen by the bracket series. All else as I've said.
I am not amused either, I forgot it was in a braketing series, but this changes nothing to it, that at 1/4000" and f:5.6 the -2 EV shot was not possible without Auto EV compensation...
03-05-2009, 02:58 PM   #15
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QuoteOriginally posted by fs999 Quote
this changes nothing to it, that at 1/4000" and f:5.6 the -2 EV shot was not possible without Auto EV compensation...
Franckly, I am now confused and don't understand your problem anymore. What did you expect, i.e., how did you want the camera behave?

Sidenote: I believe that the K20D, wehen doing an exposure bracket, changes both, aperture and exposure time, at least in M. Doesn't it do it as well in Av?
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